It is very possible that the master remembered the ball from nishi's website.

The reason they introduced the esp guys was probably to introduce the new path of gantz, aka the dinos and vampires, not just aliens. The countryside general supports this, since he is another new asset to the gantzers like the esp guys. It could have been to spice up the series, so every battle wasn't done the same way, now the bad guys die from hand-to-hand combat, esp powers, not just from being shot or squeezed.

Very nice theory. It could be true, but then again it does seem kinda cheap that you can teach other people it.

however gantz may have accidently shot himself in the foot on that one, covering up his own tracks he may have had to have taught sakata how to teach it to other people... otherwise sakata would question why he was taught it but couldnt teach anyone hence dig up memories and remember gantz... not good for gantz if sakatas chose to leave...

ehhh Guys you forgot something

You can chooze only ONE REWARD, not two. I mean if DUMBASS SAKATA would have decided to get the "SUPER WEAPON" he would have to get back to the room with 0 pts and he superweapon you know what i mean? not with THE ESP "WEAPON" and Set FREE of the gantz room.... that would be like getting two rewards at one.... kinda impossible. Unless gatnz being drunk or something or dumbass being trough gantz twice:
1) to get esp
2nd) to be free.

unless hes been thru it twice... i thought i mentioned this in another post but alas alcohol had the best of me.

but yeah i mean first time he completed it he opted for the powerful weapon (ESP) then hed have to go thru it again, and after getting thru it a second time he didnt want to risk loosing his powers or worse his life so opted to leave the gantz game

simple i think

obv that would mean he was a fucking hard ass but i think im right in thinking he has only actually been hurt so far by izumi, plus as he said himself his body is now pretty fucked and his powers arent as good anymore. but i mean christ the guy can still stop bullets...thas pretty fucking cool ya know